The present invention relates to a method for setting up or releasing a connection between a first terminal connected to a local area network and a second terminal connected to an asynchronous time division multiplexing network, hereafter abbreviated by and referred to as ATM-network, both networks being intercoupled by means of a network termination apparatus, as is further described in the non-characteristic part of claims 1,2 and 8, whereby these respective claims refer to the method either being initiated from the network termination apparatus, or from a terminal connected to the local area network or the ATM network.
The present invention also relates to a first terminal for being connected to a local area network as is described by the non-characteristic part of claim 13, to a predetermined terminal for being connected to a local area network as is referred to by the non-characteristic part of claim 14 and to a network termination apparatus for being coupled between this ATM network and this local area network, as is further described in the non-characteristic part of claims 23 and 26, for realising the respective above mentioned variants of the method.
Such a method, as well as such a network termination apparatus, are already known in the art, e.g. from the xe2x80x9cU.S. Pat. No. 5,528,590: ATM-UNI-LAN Communication method and apparatusxe2x80x9d. Therein, a method of communication between an ATM-UNI ATM network and a local area network, abbreviated by LAN, is presented, whereby in case of data transmission from the LAN side towards the ATM-UNI, reference is made in column 1, line 35 to a connection request generated upon arrival of a data frame from a LAN terminal, requesting a controller within a communication apparatus for a connection. This prior art communication apparatus corresponds to the network termination apparatus referred to in the introductory part of claims 1,2,8,13,14 and 23 and 26 of this invention. Although not explicitly mentioned in the prior art document, this connection request is generated within the communication apparatus, since it is based upon incoming data frames transmitted from a LAN terminal to that communication apparatus. For prior art connections to be set up from a terminal connected to the ATM network to a terminal connected to the LAN network, in the prior art document a call set-up request from the ATM-UNI network is transmitted towards this communication apparatus and as well applied to the controller of this communication apparatus as is mentioned in column 1, lines 41-42. The prior art communication apparatus, includes, besides the controller, also a control unit, which operate in association with each other, to perform call processing, as stated in column 5, lines 55-60. This means that they perform the necessary signalling function for setting up the connection with the terminal connected to the ATM network. In either case, for connections to be set up from the LAN side towards the ATM or vice-versa, the prior art communication apparatus, corresponding to the network termination apparatus referenced to in the introductory part of claims 1,2,8,13,14,23 and 26, thus needs to include the necessary processing devices for terminating an ATM signalling protocol. Similarly, for releasing a connection between a terminal connected to the LAN network and a terminal connected to the ATM network, the communication apparatus of the prior art, corresponding to the network termination apparatus, also needs to perform the ATM signalling protocol for releasing this connection.
Since such a network termination apparatus is physically located at the customer""s premise, cost and maintenance are important, which in case of the prior art solution, might become an issue. Therefore a method is needed whereby the complexity and consequently the cost and maintenance cost, of the network termination apparatus is reduced.
An object of the present invention is therefore to provide a method for setting up or respectively releasing a connection between a terminal connected to one network type, local area or ATM, and another terminal connected to the other network type, as well as a network termination apparatus intercoupling both networks, of the above known type, but whereby the complexity of this network termination apparatus is significantly reduced with respect to the prior art solution.
According to the invention, this object is achieved due to the fact that said method is further realised as is described in the characteristic parts of respective claims 1,2 and 8, that a predetermined terminal coupled to said local area network, is further adapted in accordance to claim 14, that the network termination apparatus is further adapted in accordance to claims 23 and 26 and that, for the method initiated from the local area network side as is described in claim 2, a first terminal coupled to said local area network is further adapted in accordance to claim 13.
In this way, a connection set-up request message or a connection release request message, generated by said network termination apparatus for requesting to set up or to release a connection between a first terminal connected to the local area network and a second terminal connected to the ATM network, is now no longer directed towards a controller within the network termination apparatus, but towards a predetermined terminal, connected to the local area network and which is adapted to terminate an ATM signalling protocol, as is explained in claims 1 and 23. As a result, the complexity and consequently, the cost of the network termination apparatus is significantly reduced.
In a variant of the method, the first terminal is itself adapted to generate this request for setting up or for releasing this connection, and to transmit its own generated LAN connection set-up or release request message towards said predetermined terminal, as is explained in claims 2 and 13. Again in this case the network termination apparatus can be kept simple.
Similarly, signalling protocol messages, transmitted from the ATM network for setting up or releasing a connection between a second terminal connected to the ATM network and a first terminal connected to the local area network, are no longer terminated within the network termination apparatus, but are merely converted in this apparatus into corresponding local area network messages which are then consecutively transferred towards the predetermined terminal connected to the local area network, adapted for terminating the some ATM signalling protocol, as is explained in method claim 8 and network termination arrangement claim 26. Upon receipt of these local area network messages consisting of converted ATM signalling protocol messages, this predetermined terminal will in its turn send adequate ATM messages for performing the signalling protocol, back to the network termination apparatus.
In each case, the ATM signalling protocol termination is performed in this predetermined terminal at the local area network side, as is stated in claim 14, thereby omitting the necessary processing devices for terminating an ATM signalling protocol in the network termination apparatus, thus seriously reducing the complexity of this apparatus, and consequently the cost and maintenance of it. A second conversion means for converting back and forth between ATM messages and local area network message, and for distinguishing between incoming ATM messages these ATM messages pertaining to an ATM signalling protocol, was already included and described in the prior art network adaptation apparatus. Therefore an extra functionality required in the network adaptation apparatus with respect to the prior art, is the conversion of these distinguished ATM signalling protocol messages into corresponding local area network messages, for further transmission towards the predetermined terminal, as is stated by claim 26. This added functional step hardly requires extra hardware or processing power. In case the request is generated in the network termination apparatus itself, as was the case in the prior art arrangement, this request is now to be generated as a local area network message, and to be directed towards the predetermined terminal, in stead of internally being handled within the network termination apparatus. This is explained in claim 23, these steps again requiring little additional hardware or processing power.
On the other hand, a predetermined terminal connected to the local area network, needs to be equipped for performing the ATM signalling protocol termination, as stated by claim 14. Since however, at the time of the invention, the majority of all terminals connected to any local area network, are already equipped with very powerful processing devices, the step of upgrading a predetermined one of them with an ATM signalling protocol termination functionality, represents much less impact on the hardware, compared to the processing power that is necessary for implementing this function in the network termination apparatus. Indeed, the already available processing power in one of these LAN terminals can be used or shared for performing this function. Only a small software module containing the necessary instructions for addressing and triggering the processor for performing this functionality is needed. On the contrary, as already mentioned, implementing the ATM protocol signalling termination functionality in the network termination apparatus, not only requires such a software module but also the processing devices to be installed, thus presenting a much higher cost compared to the solution of the invention which makes use of already installed processing power in local area network terminals.
Another characteristic feature of the present invention is that as an alternative, also the predetermined terminal itself can take the initiative for setting up or releasing a call with a terminal at the ATM side, as is explicitly indicated by claims 3, 16 and 24, or that this terminal may as well be the one to which an ATM terminal wants to set-up a connection or release an existing connection with, as is mentioned by claim 9 and claim 25.
Yet another characteristic feature of the present invention is described method claims 4 and 11, whereby said predetermined terminal is further adapted as is described in claim 19 and whereby said network termination apparatus is further adapted as is described in claim 25.
In this way, since the ATM signalling protocol means included within the predetermined terminal generates ATM messages, which cannot be properly transmitted on a legacy LAN interface means of a local area network, this predetermined terminal includes a first conversion means adapted for converting the ATM messages of the ATM signalling protocol into corresponding legacy LAN messages or LAN frames, and for further transmitting them towards the network termination apparatus.
On the other hand, the network termination apparatus is also to be adapted to distinguish between incoming local area messages, these that are converted ATM signalling protocol messages, for then reconverting them into the original ATM signalling protocol messages for transmission towards the ATM network, as is stated in claim 25.
Yet another characteristic feature of the present invention is mentioned in method claims 6 and 10, whereby the predetermined terminal is further adapted as is described in claims 20 to 22.
In this way, incoming local area network messages consisting of converted ATM signalling protocol messages are re-converted by the first conversion means into the original ATM signalling protocol messages, for further forwarding to the ATM signalling protocol means within the predetermined terminal.
In some embodiments, as will be explained more into detail in the descriptive part of this document, the predetermined terminal includes a demultiplexer means since some of the incoming local area messages, such as for instance the connection set-up or release request messages, are directly transmitted towards the ATM signalling protocol means, whereas returning messages of the signalling protocol, in local area network format, in some variants of the method, first have to be directed towards the first conversion means.